1. Field of the Invention
The present invention relates to a liquid for a liquid lens. More specifically, the present invention relates to a liquid for a liquid lens comprising an electrolyte solution and an insulating solution, compositions of the electrolyte solution and the insulating solution, and a liquid lens module comprising the liquid for a liquid lens.
2. Description of the Related Art
A great deal of research has been concentrated on liquid lenses based on the electrowetting phenomenon since the beginning of the twenty-first century. Liquid lenses are currently used in various application fields. “Electrowetting” is a phenomenon wherein the surface tension of a liquid is altered using electrical charges present at the interface of the liquid. The electrowetting phenomenon may be utilized to handle microliquids and microparticles present in liquids.
Methods for producing liquid lenses for auto focus (A/F) using the electrowetting phenomenon have the advantages of reduced electric power consumption and miniaturization of liquid lenses, compared to conventional mechanical production methods. Based on these advantages, efforts to produce liquid lenses on an industrial scale have been rapidly made. The electrowetting phenomenon is currently utilized in a wide variety of applications, including display devices, optical devices and micro-electromechanical systems (MEMSs).
However, liquid lenses have not yet been put to practical use. Two major obstacles to the successful commercialization of liquid lenses are incomplete mechanical joining of elements and possibility of mixing between two solutions after a reliability test at a high temperature (+85° C.) for 96 hours or more.
The mechanism of the electrowetting phenomenon is not clearly established, and a liquid lens with superior high- and low-temperature reliability has not hitherto been reported. Although a number of patent applications describe mechanical constitutions of liquid lenses using the electrowetting phenomenon, they fail to disclose liquid compositions of the liquid lenses. Moreover, no mention is made in these patent applications about liquid compositions for liquid lenses that can primarily prevent the possibility of mixing between an electrolyte solution and an insulating solution at room temperature while taking into consideration the control of mixing between the two solutions arising after a reliability test at a high temperature.
Liquids for liquid lenses comprise an electrically conductive electrolyte solution and an electrically insulating solution. The two solutions must have the same density and a large difference in refractive index. In addition, the two solutions must have suitable viscosity and surface tension, which are requirements for the production and realization of lenses in a simple manner. For commercialization of liquid lenses, there must be no mixing between the two solutions after a reliability test at a high temperature (+85° C.) for 96 hours or more. However, chemical and physical reactions between the two solutions after a reliability test at a high temperature induce changes in the physical properties of the solutions, thus making it difficult to achieve high reliability of lenses.